Off-road enthusiasts are celebrating a compromise that drastically scales back an expansion of the Twentynine Palms Marine base and retains most of the Johnson Valley for recreational use.

The 188,000-acre expanse of desert between Yucca Valley and Barstow is prized by both sides — off-roaders for the boulders, dry lake beds and wide open terrain, and the military for the remote, limitless space ideal for training maneuvers.

Johnson Valley is the largest off-highway vehicle area in the United States, drawing about 200,000 visitors annually and pumping an estimated $71 million a year into the local economy.

Under the law passed by Congress late Tuesday, 99,870 acres will remain part of the Johnson Valley Off-Highway Vehicle Recreation Area and be overseen by the U.S. Bureau of Land Management. That includes 56,000 acres of land to be borrowed by the Marine Corps up to twice a year for a total of 60 days.

The base expansion will cover 88,130 acres once reserved for off-roading. That is a little less than half of the 168,000 acres originally eyed by the military for simulated battle training in which Marines approach a single target from three different corridors.

Fred Wiley is treasurer of the California Motorized Recreational Council, a lobbying group made up of the eight largest off-highway vehicle groups in California that spent more than $1 million fighting to keep the Johnson Valley open.

The BLM’s continued management of the 56,000 acres of “shared” land was critical to the off-highway vehicle community, he said. Had the military remained in control, there likely would have been lost ordnance and the land would have been closed for safety reasons, Wiley said.

On the shared land, the Marines will not be able to use explosives that might not detonate immediately, creating a danger for off-roaders who might use the area. The prohibition includes projectiles larger than .50 calibers. The BLM will grant a use permit for the planned exercises, and an explosive ordnance device team will go through and make sure the area is cleaned up.

Capt. Justin Smith, spokesman for the Twentynine Palms Marine Corps Air Ground Combat Center, said the expansion will allow for more effective, realistic exercises instead of classroom instruction and simulation. Marines must train the way they fight, he said.

The Marine Corps command issued a statement on the compromise: “The Marine Corps will now be able to conduct fully integrated, live-fire exercises based on current training requirements, while still preserving safe public access for Off-Highway Vehicle recreation in Johnson Valley.”

Under an earlier military proposal, only 20,000 acres of the off-road play area would have remained open to the public year-round. The off-road community would have lost access to an area known as the Hammers, boulder fields that serve as the main attraction for the King of the Hammers, a 182-mile off-road race that takes place every February and draws about 35,000 people.

The final deal includes the front and back side of the Hammers, Spooners, Aftershock, Sunbonnet, the Riffle Monument and The Rockpile, a memorial to the eight people killed at the Cal 200 off-road race in 2010. The public also will have access to most of the Fry Mountains and all of Soggy Dry Lake and Emerson Dry Lake.

Transfer of the 88,000 acres to the Marine Corps begins immediately, but the military will have to purchase private land holdings in the expansion area, officials said.

The compromise pushed by Rep. Paul Cook, R-Yucca Valley, was approved as part of the National Defense Authorization Act.

“After years in which off-roaders have lived in fear of the closure of Johnson Valley, this permanently ends the threat of base expansion into off-road areas,” said Cook, a former Marine colonel who was stationed at the Twentynine Palms base.

Greg Rogers, a longtime off-roader from Yucca Valley, hailed the compromise that will allow him to continue using the area with his family. Rogers and his four children ride their rock crawlers, quads and dune buggies in Johnson Valley 10 to 20 times a year, he said.

“There is a huge number of people that use this area,” he said. “It would have been a disaster if we had lost it.”